Not a big deal but -
CFAI curriculum is a little ambiguous on this point. On one hand, they assume that alpha + beta = 1 in the GDP growth equation
%DY = %DTFP + alpha * %DL + (1-alpha)*%DK (where alpha = input elasticity to labor, L = labor, K = capital, I might have switched the convention for alpha and 1-alpha in case alpha usually applies to capital)
On the other hand, they assume that alpha = 1 and beta = “don’t care” as in
"GK took the historical 2 percent per year U.S. labor productivity growth rate as their forecast. Using a U.S. population growth forecast of 0.8 percent and assuming a 0.2 percentage point increase in the labor force participation rate, the forecast of the labor supply growth rate was 1 percent per year. The overall real GDP growth estimate of 2% + 1% = 3% was within the 2.7 percent to 3.6 percent range of forecasts by economists. " (vol 3 page(33)).